MAPPING AND CLONING OF THE BLOOM'S SYNDROME LOCUS

布鲁姆综合征(BS)是一种常染色体隐性遗传性疾病 临床上由生长缺陷、免疫缺陷、生育力下降和 极易患上各种类型的癌症 网站。尽管该基因被认为与某种核方式有关 在维持基因组稳定性的同时，BS的主要缺陷并没有 已被确认身份。拟议的工作的目的是绘制和克隆 布卢姆综合征基因座这一目标将由 按计划行事。 1.利用连锁分析对15号染色体上的BLm基因座进行亚定位 使用血缘图谱。 2.从该区域分离高度多态的DNA标记 通过从辐射减少的DNA片段中克隆DNA片段来连接(BLM区域) 杂交种和显微切割的染色体。 3.通过以下方式细化这些标志在BLM区域的地图位置 血缘作图、连锁-不平衡作图和远程作图 限制映射。 4.用YAC(酵母人工染色体)分离BLM区 由3中定义的最接近BLm的标记识别。 5.确定BLM的候选对象，使用DNA介导性转化来 检测其纠正BS细胞高姐妹染色单体交换表型的能力。成为 检测将是(A)整个YAC的DNA和(B)使用YAC鉴定的cDNAs 作为杂交探针。 6.通过鉴定候选基因的突变(S)来确定候选基因 Bloom综合征患者BLM基因座分子水平的研究 目标的实现将提供关于 DNA复制和修复的关键方面。这一知识将导致 了解野生型BLM基因的活性，BLM基因的作用 突变的BLM基因座的缺陷基因产物以及突变是如何发生的 基因与临床表型有关。以目前的进步 人类遗传学领域中的“染色体断裂综合征” 作为一个群体，似乎与DNA复制和修复有关--以及 哪个BS是原型-知识的总和可能会产生一个 这一复杂过程的完整和及时的完整视图，并在 从更广泛的意义上讲，体细胞维持遗传稳定性的方式。

Bloom's syndrome (BS) is an autosomal recessive disorder characterized clinically by growth deficiency, immunodeficiency, reduced fertility, and an enormous predisposition to cancer of a wide variety of types and sites. Although the gene is believed to be involved in some nuclear way with maintenance of genomic stability, the primary defect in BS has not been identified. The purpose of the work proposed is to map and clone the Bloom's syndrome locus, BLM. this goal will be accomplished by the following plan. 1.Sub-localize the BLM locus on chromosome No. 15 by linkage analysis using consanguinity mapping. 2. Isolate highly polymorphic DNA markers from the region defined by the linkage (the BLM region) by cloning DNA segments from radiation-reduced hybrids and microdissected chromosomes. 3. Refine the map location of these markers in the BLM region by consanguinity mapping, linkage-disequilibrium mapping, and long-range restriction mapping. 4. Isolate the BLM region using YACs (yeast artificial chromosomes) identified by the markers closest to BLM as defined in 3. 5. Identify candidates for BLM, employing DNA-mediated transformation to test their ability to correct the high-SCE phenotype of BS cells. To be tested will be (a) DNA from whole YACs and (b) cDNA identified using YACs as hybridization probes. 6. Confirm a candidate gene by identification of mutation(s) at the molecular level in the BLM locus in individuals with Bloom's syndrome. The fulfillment of the goal will provide fundamental knowledge about a key aspect of DNA replication and repair. this knowledge will lead to understanding the activity of the wild type BLM gene, the role of the defective gene product from the mutated BLM locus, and how the mutated gene is involved in the clinical phenotype. With the current advances in the field of human genetics on the "chromosome-breakage syndromes" that as a group appear related to DNA replication and repair - and of which BS is the prototype - the sum total of knowledge may yield an integrated and in time complete view of this complex process, and in a broader sense, the way somatic cells maintain genetic stability.